DESCRIPTION: H. pylori is a major cause of gastrointestinal disease worldwide. Recently, several putative virulence factors of Helicobacter organisms have been identified. Characterization of these determinants and investigation into their mechanisms of action is an important area of study in Helicobacter pathogenesis. Molecular biological techniques have allowed research in this field to progress rapidly in both the identification and characterization of virulence factors and in the ability to study these determinants in vivo. The H. mustelae ferret model has been thoroughly characterized and is the only naturally-infected animal model to develop ulcer disease. Several isogenic mutant strains of H. mustelae lacking individual virulence factors have been constructed and offer a unique opportunity to investigate the mechanisms of Helicobacter pathogenesis. The objectives of this research are to characterize the virulence factors of H. mustelae and to conduct in vivo infection studies using isogenic mutant strains of H. mustelae in the ferret model. Characterization of the effects of individual virulence determinants will increase our understanding of Helicobacter pathogenesis and assist in therapeutic and preventative measures.